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https://issues.apache.org/jira/browse/KNOX-1997?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16924046#comment-16924046
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Rajat Goel commented on KNOX-1997:
----------------------------------
Thanks [~smore] . I have raised the following PR for this issue:
[https://github.com/apache/knox/pull/143.]
> For websocket connections, seeing java.lang.NullPointerException when a data
> frame arrives on websocket while connection is still being setup
> ---------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: KNOX-1997
> URL: https://issues.apache.org/jira/browse/KNOX-1997
> Project: Apache Knox
> Issue Type: Bug
> Components: Server
> Affects Versions: 1.0.0, 1.1.0, 1.2.0, 1.3.0
> Environment: HDP 3.1.0
> Reporter: Rajat Goel
> Assignee: Rajat Goel
> Priority: Major
> Fix For: 1.4.0
>
> Attachments: KNOX-1997.patch, gateway.log_26Aug.gz
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> I am seeing following exception in Knox gateway logs:
> {code:java}
> 2019-08-23 12:43:46,347 WARN websockets.ProxyInboundClient
> (AbstractEventDriver.java:unhandled(251)) - Unhandled Error (closing
> connection)_
> java.lang.NullPointerException
> at
> org.apache.knox.gateway.websockets.ProxyWebSocketAdapter$3.onMessageText(ProxyWebSocketAdapter.java:260)
> at
> org.apache.knox.gateway.websockets.ProxyInboundClient$2.onMessage(ProxyInboundClient.java:87)
> at
> org.apache.knox.gateway.websockets.ProxyInboundClient$2.onMessage(ProxyInboundClient.java:78)
> at
> org.eclipse.jetty.websocket.jsr356.messages.TextWholeMessage.messageComplete(TextWholeMessage.java:56)
> at
> org.eclipse.jetty.websocket.jsr356.endpoints.JsrEndpointEventDriver.onTextFrame(JsrEndpointEventDriver.java:218)
> at
> org.eclipse.jetty.websocket.common.events.AbstractEventDriver.incomingFrame(AbstractEventDriver.java:162)
> at
> org.eclipse.jetty.websocket.common.WebSocketSession.incomingFrame(WebSocketSession.java:476)
> at
> org.eclipse.jetty.websocket.common.extensions.ExtensionStack.incomingFrame(ExtensionStack.java:220)
> at org.eclipse.jetty.websocket.common.Parser.notifyFrame(Parser.java:219)
> at org.eclipse.jetty.websocket.common.Parser.parse(Parser.java:244)
> at
> org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onConnectionStateChange(AbstractWebSocketConnection.java:337)
> at
> org.eclipse.jetty.websocket.common.io.IOState.notifyStateListeners(IOState.java:184)
> at org.eclipse.jetty.websocket.common.io.IOState.onOpened(IOState.java:447)
> at
> org.eclipse.jetty.websocket.common.WebSocketSession.open(WebSocketSession.java:619)
> at
> org.eclipse.jetty.websocket.common.WebSocketSession.onOpened(WebSocketSession.java:544)
> at
> org.eclipse.jetty.io.AbstractConnection.onOpened(AbstractConnection.java:209)
> at
> org.eclipse.jetty.io.AbstractConnection.onOpen(AbstractConnection.java:202)
> at
> org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onOpen(AbstractWebSocketConnection.java:446)
> at org.eclipse.jetty.io.AbstractEndPoint.upgrade(AbstractEndPoint.java:440)
> at
> org.eclipse.jetty.websocket.client.WebSocketUpgradeRequest.upgrade(WebSocketUpgradeRequest.java:624)
> at
> org.eclipse.jetty.client.http.HttpChannelOverHTTP.exchangeTerminating(HttpChannelOverHTTP.java:118)
> at
> org.eclipse.jetty.client.HttpReceiver.terminateResponse(HttpReceiver.java:462)
> at
> org.eclipse.jetty.client.HttpReceiver.responseSuccess(HttpReceiver.java:416)
> {code}
> I added more debug logs in Knox to analyze the issue and observed following
> was happening:
> * Knox generates proper URL for backend websocket connection
> {code:java}
> 2019-08-23 12:43:46,068 DEBUG gateway.websockets
> (GatewayWebsocketHandler.java:createWebSocket(148)) - Message: Rajat ..
> backednUrl =
> ws://rafd001-mst-01.cloud.in.guavus.com:11011/_sock/411/anq2kfzp/websocket{code}
> * Websocket upgrade successful at HTTP protocol layer. Knox starts setting
> up its session management internal data structures for this connection
> {code:java}
> 2019-08-23 12:43:46,313 DEBUG client.HttpReceiver
> (HttpReceiver.java:responseSuccess(403)) - Response success
> HttpResponse[HTTP/1.1 101 Switching Protocols]@708f1c60
> _2019-08-23 12:43:46,324 DEBUG common.WebSocketSession
> (WebSocketSession.java:doStart(248)) - starting -
> WebSocketSession[websocket=JsrEndpointEventDriver[org.apache.knox.gateway.websockets.ProxyInboundClient],behavior=CLIENT,connection=WebSocketClientConnection@1528d316::SocketChannelEndPoint@10d45033
> {[rafd001-mst-01.cloud.in.guavus.com/192.168.133.69:11011|http://rafd001-mst-01.cloud.in.guavus.com/192.168.133.69:11011]<->/[192.168.133.69:50702|http://192.168.133.69:50702/],OPEN,fill=-,flush=-,to=23/300000}
> {io=0/0,kio=0,kro=1} >
> r:rafd001-mst-01.cloud.in.guavus.com/192.168.133.69:11011,closed=false)=>HttpChannelOverHTTP@26de2594(exchange=HttpExchange@7e8b6268
> req=TERMINATED/null@null
> res=TERMINATED/null@null)[send=HttpSenderOverHTTP@73b692d4(req=QUEUED,snd=COMPLETED,failure=null)[HttpGenerator@4e3bb764\{s=START}],recv=HttpReceiverOverHTTP@7d5a172b(rsp=IDLE,failure=null)[HttpParser\{s=START,0
>
> of1}]],remote=null,incoming=JsrEndpointEventDriver[org.apache.knox.gateway.websockets.ProxyInboundClient],outgoing=ExtensionStack[queueSize=0,extensions=[],incoming=org.eclipse.jetty.websocket.jsr356.JsrSession,outgoing=org.eclipse.jetty.websocket.client.io.WebSocketClientConnection]]{code}
> * A data frame arrives on the connection from CDAP backend and Knox starts
> processing it in a separate thread but internal data structures have not yet
> been established fully:
> {code:java}
> 2019-08-23 12:43:46,346 DEBUG gateway.websockets
> (ProxyWebSocketAdapter.java:onMessageText(257)) - Message: Rajat .. In
> onMessageText .. remote is nulll
> 2019-08-23 12:43:46,347 WARN websockets.ProxyInboundClient
> (AbstractEventDriver.java:unhandled(251)) - Unhandled Error (closing
> connection)
> java.lang.NullPointerException
> at
> org.apache.knox.gateway.websockets.ProxyWebSocketAdapter$3.onMessageText(ProxyWebSocketAdapter.java:260)
> at
> org.apache.knox.gateway.websockets.ProxyInboundClient$2.onMessage(ProxyInboundClient.java:87)
> at
> org.apache.knox.gateway.websockets.ProxyInboundClient$2.onMessage(ProxyInboundClient.java:78){code}
> * As a result of this exception, Knox starts closing this connection as well
> as connection with front end.
> {code:java}
> 2019-08-23 12:43:46,347 DEBUG gateway.websockets
> (ProxyWebSocketAdapter.java:onError(246)) - Message: Rajat .. inside onError
> 2019-08-23 12:43:46,348 DEBUG gateway.websockets
> (ProxyWebSocketAdapter.java:cleanupOnError(183)) - Message: Rajat .. inside
> cleanupOnError
> 2019-08-23 12:43:46,348 ERROR gateway.websockets
> (ProxyWebSocketAdapter.java:cleanupOnError(185)) - Error:
> java.lang.NullPointerException
> 2019-08-23 12:43:46,349 DEBUG gateway.websockets
> (ProxyWebSocketAdapter.java:closeQuietly(294)) - Message: Rajat .. in
> closeQuietly{code}
> * Internal data structures are now setup in the other thread
> {code:java}
> 2019-08-23 12:43:46,356 DEBUG gateway.websockets
> (ProxyWebSocketAdapter.java:onWebSocketConnect(113)) - Message: Rajat ...
> frontEndSession =
> WebSocketSession[websocket=JettyListenerEventDriver[org.apache.knox.gateway.websockets.ProxyWebSocketAdapter],behavior=SERVER,connection=WebSocketServerConnection@151585ba::DecryptedEndPoint@4463419a
>
> {/[192.168.110.254:61755|http://192.168.110.254:61755/]<>/[192.168.133.69:8443|http://192.168.133.69:8443/],OPEN,fill=,flush=,to=423/300000}
> ,remote=WebSocketRemoteEndpoint@66632a26[batching=true],incoming=JettyListenerEventDriver[org.apache.knox.gateway.websockets.ProxyWebSocketAdapter],outgoing=ExtensionStack[queueSize=0,extensions=[permessage-deflate],incoming=org.eclipse.jetty.websocket.common.extensions.compress.PerMessageDeflateExtension,outgoing=org.eclipse.jetty.websocket.common.extensions.compress.PerMessageDeflateExtension]]
> 2019-08-23 12:43:46,358 DEBUG gateway.websockets
> (ProxyWebSocketAdapter.java:onWebSocketConnect(119)) - Message: Rajat
> ...front remote = WebSocketRemoteEndpoint@66632a26[batching=true]{code}
> * Fronted UI sees connection closed and send a new connection request.
> Looks like there is a race condition/improper synchronization between two
> Knox threads: one thread opening a websocket connection, setting up the
> connection session and the other thread processing a message/data packet sent
> by UI service backend.
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